Heat transfer elements for rotary regenerative heaters



0. F. STARK June 11, 1957 HEAT TRANSFER ELEMENTS FOR ROTARY REGENERATIVEHEATERS Filed July '22, 1954 INVIENDTOR. 1 0' F S/ar/C i d StatesPatentQ HEAT TRANSFER ELEMENTS FOR ROTARY REGENERATIVE HEATERS Conrad F.Stark, Wellsville, N. Y., assignor to The Air Preheater Corporation, NewYork,,N. Y., a corporation of New York Application July 22, 1954, SerialNo. 445,135

'6 Claims. (Cl. 257-!-1) ments in which are supported spaced metallicheat transfer plates which as the rotor turns are first exposed to astream of heatinggases and then disposed in the air passage to impartthe heat absorbed from the gases to the air. A difficulty sometimesencountered in the operation of regenerative type heaters is the foulingof the heat exchanger surfaces by fly ash or other products ofcombustion which, with the use of certain fuels and under certaincombustion conditions, may become so serious that resistance to flowthrough the spaces between the heat transfer plates is increased to thepoint where it limits the operational capacity of the heater andeventually necessitates curtailment of operation.

Heretofore, it has been customary to provide soot blowers which deliverair or steam under pressure to the tightly packed heating elements orplates to dislodge the deposits and carry them away leaving a relativelyclean body of heating elements. However, it is frequently the case thatthe amassed deposits are satisfactorily removed from the edges of theelements adjacent the soot blower While portions thereof more remotefrom the soot blowers receive insufficient cleaning fluid to effect aneflicient cleaning operation.

According to the present invention, it is therefore proposed to providepairs of mating heating elements relatively loosely packed within therespective compartments of the rotor so that when they are subjected toa fluid jet from an air or steam soot blower, the plates will attain anatural vibration causing the plates to be rapped together with greatrapidity so as to effectively dislodge deposits over the entire surfaceof each heating element including portions thereof which are remote fromthe concentrated soot blower jet and which would otherwise receivelittle or no cleaning action from a conventional soot blower.

The invention will be best understood upon reference to the followingdetailed description of an illustrative embodiment thereof when read inconjunction with the accompanying drawing in which:

Figure 1 is a sectional elevation of a rotary regenerative airpreheater;

Figure 2 is a plan view of a portion of a rotor carrying pairs of heatexchanger elements arranged according to this invention; and

Figure 3 is a plan view on a greatly enlarged scale of a section ofFigure 2 and illustrates the pair of the heat transfer plates orelements according to this invention.

As is illustrated in the drawing, the regenerative air preheater whichcontains the heat transfer plates of this invention, comprises a housing10 enclosing a rotor 11 containing metallic heat transfer plates 32 and32A (Fig- Ice ures 2 and 3) which are moved first into contact withgases enteringthrough the duct 12 for absorbing heat therefrom, and theninto contact with air entering through duct 13 to preheat the air, therotor being turned by a motor (not shown) connected to a rotor post 14.The rotor 11 comprises a cylindrical shell 15 connected by radiallyextending partitions or diaphragms 17 to. the rotor post 14 which serveto subdivide the rotor into a plurality of wedge or sector shapedcompartments 19. Sector plates 18 at the ends of the casing 10. atopposite ends of the rotor 11 are formed with alined openings as at 20for passing heating gases and air through the rotor. The flow of gas andair between sides of the rotor and the housing 10 is prevented bycircumferential seals 23 carried on the edge rims of the rotor shell 15.

The heat transferplates 32, 32A are. undulated, or corrugated, andsimilarly formed so that each of a pair of plates nests with the other.Thus a pair of plates pre sents 'a double thickness of metalconstituting a heat absorbing mass but is subjected to corrosive actionof flue gases on only two. faces, rather than four, since the platesthough loosely packed of a pair are. in substantial contact and even ifslightly separated would present a very narrow passage for gas flowcompared with the flow areas at the sides of each pair of plates.

The cleaning means for this apparatus comprises a cleaning nozzle 30disposed in the air passage opposite the heat transfer plates fordirecting jets of cleaning fluid upon them as they pass slowly beneaththe nozzle While the latter is moved from the rim of the rotor towardsthe center and then returned to the rim. Steam, air or other cleaningfluid is supplied to the cleaning nozzle from any suitable pressurizedsource of supply not here shown. After leaving the cleaning nozzle, theblast or jet of cleaning fluid is directed upon the end edge portions ofthe loosely packed heating elements 32 and 32A and the spaced dividerplates 34. As the jet of cleaning fluid strikes the end portion of thebody of heating elements, turbulence in the fluid stream is at once setup causing the loosely mounted heating elements to rapidly vibrate withthe fluid stream so as to jar loose fly ash and other deposits adheringto the entire surface thereof, thereby giving assistance to the directfluid blast emanating from the cleaning fluid jet. In this manner thefly ash and other products of combustion are readily removed from theentire surface of each heating element to thereby maintain a relativelyclean heat exchanger at a correspondingly high degree of operatingefliciency.

What I claim is:

1. In a rotary regenerative heater having a cylindrical housing formedwith parallel passages for heat exchange between gaseous fluids, a rotorin said housing carrying heat transfer elements into the passage for hotgas to absorb heat therefrom and then into the passage for fluid to beheated to impart heat thereto, said heat transfer elements comprising; aseries of nesting pairs of similarly formed heat transfer elementshaving adjacent pairs of heat transfer elements separated by planemetallic plates, said plates and nested elements being loosely containedin the rotor to permit a limited lateral vibration thereof.

2'. In a rotary regenerative heater having a cylindrical housing formedwith parallel passages for heat exchange between gaseous fluids, acylindrical rotor in said housing for carrying heat transfer plates intothe gas passage to absorb heat from the gases passing therethrough andthen to the air passage to impart heat to the air passing therethroughand radially extending partitions dividing said rotor into a pluralityof sector shaped compartments; a series of nesting pairs of heatexchanger plates in each compartment, pairs of which are looselyarranged in nesting relation in alternation with plane dividing plates;and a cleaning means mounted on the housing for movement 3 transverselyof the rotor to direct a stream of cleaning fluid onto the end faces ofsaid heating elements thereby causing them to vibrate sufficiently tojar loose any deposits clinging thereto. 1

3. In a rotary regnerative heater having a cylindrical housing formedwith parallel passages for heat exchange between gaseous fluids, acylindrical rotor in said housing for carrying heat transfer plates intothe hot gas passage to absorb heat therefrom and then into the airpassage to impart heat thereto, and radially extending partitionsdividing said rotor into a plurality of sector shaped compartments; aseries of mating pairs of heat transfer elements, pairs of which areloosely arranged in alternation with a plurality of plane dividersheets; and a cleaning nozzle mounted on said housing for movementtransversely of the rotor to direct cleaning fluid onto the heattransfer elements, the fluid stream from said nozzle causing the heattransfer elements to vibrate sufficiently to jar loose products ofcombustion clinging thereto.

4. Ina rotary regenerative heat exchanger having a cylindrical housingformed with parallel passages for the exchange of heat between fluidsflowing therethrough; a cylindrical rotor carrying heat transfer platesinto the hot gas passage to impart heat thereto and radially extendingpartitions dividing the rotor into a plurality of sector shapedcompartments; 2. series of mating pairs of formed heat transferelements, pairs of which are loosely arranged in alternation with aplurality of plane divider sheets; a cleaning nozzle mounted on saidhousing for movement transversely of the rotor to direct cleaning fluidonto the heat transfer elements carried thereby, said nozzlesimultaneously subjecting the heat transfer element to a vibratingmotion and to a flow of cleaning fluid.

5. A rotary regenerative heat exchanger as defined in claim 4 whereinthe flow of cleaning fluid from the cleaning device subjects the heattransfer element to a simultaneous rapping and purging action.

6. A rotary regenerative heat exchanger as defined in claim 4 whereinthe flow of cleaning fluid from the cleaning device simultaneouslysubjects a portion of the heat transfer element to a purging and rappingaction.

References Cited in the file of this patent UNITED STATES PATENTS2,122,176 'Herbeck' June 28, 1938 2,183,936 Karlsson et al Dec. 19, 19392,372,997 Yerrick et a1 Apr.3, 1945 2,379,506 Yerrick et a1. July 3,1945

